Innate Immunity Flashcards
What is innate immunity?
Body’s first line defence against pathogens
Tell me about the physical barriers in the human body
Innate immunity
Everything on the surface (tight junction, eyelids/lashes, epithelial cells, cilia, and mucous membrane)
Tell me about the biological barriers in the body
Innate immunity
Chemical/organismal
Bacteria, saliva, urine, tears, stomach acid, anti-microbial peptides (alpha and beta defensins in bacterial cell membranes)
What is different in the lymphatic system than the cardiovascular system?
Lymphatic vessels carry lymph
Not closed
Where are lymphocytes concentrated?
List lymphatic tissues
Lymph nodes
Lymphatic tissues - spleen, thymus, tonsils, adenoid, appendix, Peyer’s patches
Allows them to intercept microbes before they enter circulation
What is the function of lymph nodes?
Exchange lymphocytes with the lymph
Intercept microbes before they enter circulation
What is the function of appendix lymphoid tissue?
Make antibodies and sensitize T cells (released into lymph)
What is the lymphoid function of the spleen?
- Exchange lymphocytes with blood
- Lymphocytes make antibodies and sensitize T-cells
- Macrophages remove microbes and debris
What is the lymphoid function of the thymus?
- Maturation site for T lymphocytes
- Secretes thymosin
What cells are involved in innate immunity?
- Mononuclear phagocytes (macrophages, dendritic cells)
- Natural killer cells
- Mast cells
- Granulocytes (basophils, eosinophils, and neutrophils)
- Complement proteins
What are characteristic of the innate system cells?
- Highly phagocytic
- Myeloid lineage
- Respond within minutes/hrs of recognizing pathogens
- Short-lived
- Rapid response
- Non-specific
- No memory
What allows lineage tracing of myeloid cells?
Cells differentiate in tissues at different times
What receptors allow innate immune cells to recognize a pathogen?
Pattern Recognition Receptors (PRRs)
4 major types
What are the 4 major types of PRRs?
- Toll-like Receptors (TLRs)
- NOD-like Receptors (NLRs)
- C-type lectin receptors (CLRs)
- RIG-1 like receptors (RLRs)
How do PRRs work?
Recognize Pathogen-Associated Molecular Patterns (PAMPs)
PAMPs - proteins, peptides, carbs, nucleic acids on pathogen surface that the innate immune cells react to
Tell me about TLRs
Toll-like Receptors
- Transmembrane proteins in plasma membrane or endosomes
- On immune and non-immune cells
- Broad range of specificities
- Activates MAP kinase, NFkBm and IRF pathways
Tell me about NLRs
NOD-like Receptors
- Cytoplasmic receptors w many subfamilies
- recognize bacterial, viral, parasitic, and fungal PAMPs
- NOD1 and NOD2 recognize bacterial peptidoglycan
How do NLRs recognize viral and bacterial DNA?
- AIM2 detects viral and bacterial DNA
- Forms signalling complexes called inflammasomes
- Activates caspase-1-mediated processing and IL-1B and IL-18
Tell me about CLRs
C-type lectin receptors
- Transmembrane proteins in plasma membrane
- Recognize glycans on bacteria and fungal walls
- Activates kinase syk and CARD9/MALT1/Bcl-10 adapter complex
Tell me about RLRs
RIG-1 like receptors
- Cytoplasmic receptors of viral DNA
- Signal via mitochondrial adaptor protein MAVS
- Trigger antiviral responses inc type I interferon production
Which PRRs are transmembrane?
CLR - C-type lectin receptors
TLR - Toll-like receptors
What PRRs are cytoplasmic?
NLRs and RLRs
Do cells only have 1 type of PRR?
No, they usually have multiple working at the same time
- There are PRR that are specific for certain PAMPs and DAMPs
What is a consequence of PAMP-PRR interaction?
Interaction leads to downstream signalling –> inflammatory signals and get the innate immune cell ready to communicate with cells of the adaptive immune system
